Iridium Spark plugs

sfcpiet said:
Maybe, but that's not the point. Using both resistor-type plugs and caps can seriously bugger up some aftermarket ignition systems. Seems nobody wants to RTFM anymore. Maybe the modern vehicle electrical systems that seem to produce more current than the power station down the road can cope with resistors in both components. Ask NGK what they're doing for our old bangers, which do not belong to the category "comply to current legislation".

The precious metals are not about conduction, it's mostly about wear. Healthy ignition systems of any type should work quite satisfactorily with run-of-the-mill copper core plugs, they generally generate more than enough oomph for a nice fat spark at the plug. Tired, old, magneto systems with points could well benefit from the superior conductivity of silver core plugs. Iridium plugs generally have a 100000km change interval in modern engines, something not even silver or gold-palladium plugs could achieve, mine all reached the end of their useful life around the 40000km mark.

Champion N2G and N3G gold-palladium plugs are still available here and there.

Although NGK B8ES and Champion N3C pop up next to another on comparison charts world-wide, they are not the same. Much the same with NGK 9 and N2. Close... but no cigar. The NGK 8s generally require rejetting from factory specs because they run a fair bit hotter, which is then falsley blamed on "modern fuels". With the 9s, it's the other way round, they are considerably colder than the Champs. Imho, a stock Laverda will run happily on modern fuels with factory spec jetting and correct plugs, which don't even need to be Champions!

Never seen anything about NGK products that would make them "unique and superior". Only thing going for them is that there's a rack of them in every second corner-shop...

piet
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I was answering a question concerning plugs for racing..not fo road use, which I'd already said copper core plugs would be suitable for. If you have a race prepped engine, running higher compression/racing i.e flat slide carbs/ high output coils/ported heads you need the best performing plugs you can get. I've run iridium plugs for years on another 80's bike I own, and only replaced them because they had corroded externally. though I've now gone to stick coils and silver tipped plugs, as it's running at a higher spec tuning wise.
Whether plugs of one type or another run hotter than another make and require rejetting is an interesting one, due to the different factors required to make an engine run..one of those being fuel... Premium (non-ethanol)? E5? E10? All different performing fuels..Premium will be richer...ethanol contains one oxygen atom, so ethanol 'enriched' fuel burns leaner, and the more ethanol, the leaner the burn. Also you have to in to the equation air/temperature/density and altitude (affecting oxygen concentration), as well as what makes the bang.. having a plug that is operating efficiently for the way the engine has been tuned. In essence, having the 'correct' plug grade is a only an exact science if you stick to the same fuel brand/type and have the engine set up on a dyno. The road user can only run the recommended plug and adjust to a hotter or colder plug if the bike isn't running right.
With regard to the resistor plug/resistor cap? Yes, you have a point, but it does depend on what kind ignition system people have. As you said, modern or old. I've got a Witt system on my RGA Jota that I'm rebuilding so I'll be using non-resistor plugs, or resistor plugs and non-resistor caps.
 
Flame front velocity is a significant factor, almost impossible to obtain a working figure these days. Flame front velocity has a significant effect on advance ( strictly "retard" from forward reference, cannot have advance on something that has not occurred, pet hate of mine, sic ).

( actual ) Fuel chemistry, air/fuel cylinder load is highly variable these days. As it may be of interest. j
 
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